linux-kernel - Re: MTD EEPROM support and driver integration

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Date:	Sat, 6 Jul 2013 10:28:04 +0200
From:	Maxime Ripard <maxime.ripard@...e-electrons.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Artem Bityutskiy <dedekind1@...il.com>,
	Shawn Guo <shawn.guo@...aro.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	oliver@...inagl.nl, linux-mtd@...ts.infradead.org
Subject: Re: MTD EEPROM support and driver integration

On Sat, Jul 06, 2013 at 12:33:13AM +0200, Arnd Bergmann wrote:
> On Saturday 06 July 2013, Maxime Ripard wrote:
> > > My first thought is that it should be more generic than that and not
> > > have the mac address hardcoded as the purpose. We could possibly use
> > > regmap as the in-kernel interface, and come up with a more generic
> > > way of referring to registers in another device node.
> > 
> > Hmm, I maybe wasn't as clear as I wanted. Here mac-storage was just an
> > example. It should indeed be completely generic, and a device could have
> > several "storage source" defined, each driver knowing what property it
> > would need, pretty much like what's done currently for the regulators
> > for example.
> > 
> > We will have such a use case anyway for the Allwinner stuff, since the
> > fuses can be used for several thing, including storing the SoC ID,
> > serial numbers, and so on.
> 
> Ah, I see. In general, we have two ways of expressing the same thing
> here:
> 
> a) like interrupts, regs, dmas, clocks, pinctrl, reset, pwm: fixed property names
> 
> 	regmap = <&at25 0xstart 0xlen>;
> 	regmap-names = "mac-address";
> 
> b) like gpio, regulator: variable property names
> 
> 	mac-storage = <&at25 0xstart 0xlen>;
> 
> It's unfortunate that we already have examples of both. They are largely
> equivalent, but the tendency is towards the first.

I don't have a strong feeling for one against another, so whatever works
best. Both solutions will be a huge improvement anyway :)

Just out of curiosity, is there any advantages besides having a fixed
property name to the first solution?

Thanks,
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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